Chemokines are an emerging super-family of small secreted cytokines that are structurally and functionally related. All chemokines exhibit 25 to 75% homology at the amino acid level and contain spatially conserved cysteine residues as do the polypeptides of the present invention. Members of the “C-X-C branch” (according to the position of the first two cysteines in the conserved motif), also known as neutrophil-activating peptide (NAP)/IL-8 family, exert pro-inflammatory activity mainly through their action on neutrophils (e.g., IL-8 and NAP-2), whereas members of the “C—C branch” family appear to attract certain mononuclear cells. Members of the “C—C branch” include PF4, MIPs, MCPs, and the chemokine polypeptides of the present invention.
Numerous biological activities have been assigned to this chemokine family. The macrophage inflammatory protein 1α and 1β are chemotactic for distinct lymphocyte populations and monocytes (Schall, T. J., Cytokine, 3:165 (1991)), while MCP-1 has been described as a specific monocyte chemo-attractant (Matsushima, K., et al., J. Exp. Med., 169:1485 (1989)). The common function of this chemokine family is their ability to stimulate chemotactic migration of distinct sets of cells, for example, immune cells (leukocytes) and fibroblasts. These chemokines are also able to activate certain cells in this family.
The immune cells which are responsive to the chemokines have a vast number of in vivo functions and therefore their regulation by such chemokines is an important area in the treatment of disease.
For example, eosinophils destroy parasites to lessen parasitic infection. Eosinophils are also responsible for chronic inflammation in the airways of the respiratory system. Macrophages are responsible for suppressing tumor formation in vertebrates. Further, basophils release histamine which may play an important role in allergic inflammation. Accordingly, promoting and inhibiting such cells, has wide therapeutic application.